what to do at end of life

[Dwight Elvey]

Here in California, we are required to have a CO detector in our house by law. These run for about 7 to 10 years, depending on the manufacture and then they are programmed to quit.
They give out a message on the LCD as End of Life or some such and start making annoying beeps.
Just curious, I open one up to see what makes them tick. It looks like they run on a 32Khz crystal and have a PIC16LF1933 processor. I assume these can be reprogrammed for other purposes ( I'm not sure what right now ). The CO sensor looks like a large can but that is the part that ages.
It has two switches, two leds, small LCD and a piezo speaker. There is a coil to make the oscilator for the piezo with a number of transistors, resistors and capacitors.
Now what could one do to give this uC a new life.
Dwight

[ClassicHasClass]

Y'know, the title of this thread gave me a totally different impression!

[jltursan]

Hey Dwight, what about adding "CO detectors: ..." to the beggining of the thread subject?

To say the least, the subject has scared me a bit at first...

[Chuck(G)]

As far as the PIC16LF1933, not much memory, not very fast. On the older CO detectors, the AtoD and DtoA chips can be moderatively interesting.. The MCU not so much.

[2icebitn]

The term EOL has common usage in the industry.

[Ole Juul]

The term EOL has common usage in the industry.

Agreed. It is indeed plain English and no interpretation is needed. However, a subject is still required in order to give it meaning. Dwight's post is interesting though.

[commodorejohn]

Rip out the guts and leave it on the wall pretending to be functional?

Of course, I don't have any dependents to worry about, but as far as I'm concerned, I'll take asphyxiation over having to deal with the gorram nagging beepers. (See also: smoke alarms.)

[KC9UDX]

Except that EOL doesn't mean End of Life, it means End of the Line, as in railroad track.

The trouble with modifying something like this is that the only real reason to have them is so your insurance isn't voided when you need it. And having a 12 year old detector is just as bad as having none.

[rmay635703]

I think he wants to just have fun seeing what the pic can do by itself,
He likely has another CO detector

[Dwight Elvey]

Sorry about the tile ( no not really ). I just thought it was fun that the alarm has the PIC processor in it. I've not got a new one yet. It just gave out a couple days ago. It is a small slow processor but it is still something that could take a different project.
Any way, it got your attention.
I'm not sure how the detection part works. There is no A/D. It is just a bunch of discrete parts. It has twp areas marked WAX AREA-A and WAX AREA-B. They have a thin coat of what looks to be wax. I'm guessing these areas use the wax as insulation areas. My guess is that it charges up the CO cell and then waits to see how fast it discharges. Every thing is made with three lead transistors and there are two small 5 lead surface mount marked U2 and U4. The U4 one is covered in a thin layer of wax and hard to make out a label. U2 looks like a voltage regulator of some type. It is associated with the piezo and coil. One wonders if the piezo and coil may be used for a high voltage generator. It could be used at a high frequency for the high voltage and a low frequency for the low voltage?? Nah, it is just part of the sounder circuit.
Dwight